Systems and methods for excluding Relay Nodes from Multi-User Multiple-Input-Multiple-Output (MU-MIMO) pairing

ABSTRACT

Systems and methods are described for selecting relay nodes for Single-User Multiple-Input-Multiple Output (SU-MIMO). A channel orthogonality and Signal-to-Interference-Plus-Noise Ratio (SINR) of a plurality of wireless devices located in a geographic area of an access node is determined. A relay-capable status of the plurality of wireless devices is determined. Non-relay capable wireless devices located in the geographic area are excluded from SU-MIMO. From the plurality of wireless devices, relay-capable wireless devices are selected for SU-MIMO. The selected relay-capable wireless devices are prioritized for SU-MIMO based on a channel orthogonality and SINR meeting a set threshold.

This patent application is a continuation of U.S. patent applicationSer. No. 15/082,258, filed on Mar. 28, 2016, which is incorporated byreference in its entirety for all purposes.

TECHNICAL BACKGROUND

As wireless networks evolve, the demand for high Quality of Service(“QoS”) coupled with, for example, a shortage of wireless spectrum,makes it challenging for network operators to meet user demand. Oneapproach, in Heterogeneous Networks (“HetNet”), is exploitation of RelayNodes (“RNs”), e.g., low-power nodes and/or relay-capable users, atcell-edges, “hotspots,” or coverage “holes” of the network to boostspatial coverage and/or cell-edge capacity. HetNets may also implementwireless technologies such as Single-User and/or Multi-UserMultiple-Input-Multiple-Output (“SU/MU-MIMO”), OrthogonalFrequency-Division Multiplexing (“OFDM”), and/or advanced errorcorrection techniques to achieve throughput gains.

Under a typical MU-MIMO scheme, users may be prioritized for MU-MIMOpairing based on, for example, channel orthogonality and/or aSignal-to-Interference-Plus-Noise Ratio (“SINR”), regardless of a RNstatus, which may reduce efficiencies and decrease overall cellthroughput.

OVERVIEW

Systems and methods are described for enabling Multi-UserMultiple-Input-Multiple-Output (“MU-MIMO) pairing of wireless devicesserved by an access node. In one instance, a channel orthogonality andSignal-to-Interference-Plus-Noise Ratio (“SINR”) of a plurality ofwireless devices located in a geographic area served by the access nodeis determined. Relay-capable wireless devices located in the geographicarea are excluded from MU-MIMO pairing. From the plurality of wirelessdevices, non-relay capable wireless devices are selected for MU-MIMOpairing. The non-relay capable wireless devices selected for MU-MIMOpairing are prioritized based on a channel orthogonality and SINRmeeting a set threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an exemplary communication system 100 for excludingRelay Nodes (“RNs”) from Multi-User Multiple-Input-Multiple-Output(“MU-MIMO”) pairing.

FIG. 1B illustrates a portion of the exemplary system 100 illustrated inFIG. 1A for excluding RNs from MU-MIMO pairing.

FIG. 1C illustrates an access node of the exemplary system 100illustrated in FIG. 1A operating in Single-User MIMO (“SU-MIMO”) mode.

FIG. 1D illustrates an access node of the exemplary system 100illustrated in FIG. 1A operating in MU-MIMO mode.

FIG. 1E illustrates bits used for signaling in SU-MIMO and MU-MIMO mode.

FIG. 2 illustrates an exemplary method for excluding RNs from MU-MIMOpairing.

FIG. 3 illustrates a portion of an exemplary communication system forexcluding RNs from MU-MIMO pairing.

FIG. 4 illustrates another exemplary method for excluding RNs fromMU-MIMO pairing.

FIG. 5 illustrates an exemplary processing node.

DETAILED DESCRIPTION

FIG. 1A illustrates an exemplary communication system 100 for excludingRelay Nodes (“RNs”) from Multi-User Multiple-Input-Multiple-Output(“MU-MIMO”) pairing. FIG. 1B illustrates a portion of the exemplarysystem 100 illustrated in FIG. 1A for excluding RNs from MU-MIMOpairing. FIG. 1C illustrates an access node of the exemplary system 100illustrated in FIG. 1A operating in Single-User MIMO (“SU-MIMO”) mode.FIG. 1D illustrates an access node of the exemplary system 100illustrated in FIG. 1A operating in MU-MIMO mode. FIG. 1E illustratesbits used for signaling in SU-MIMO and MU-MIMO mode.

In operation, Relay Nodes (“RNs”) may be exploited in HeterogeneousNetworks (“HetNet”) at cell-edges, “hotspots,” and/or coverage “holes”of geographical areas 148, 152 of high-powered, large scale accessnodes, for example, donor access nodes (“DeNBs”) 110 and/or 112, toboost spatial coverage and/or cell-edge capacity. For example, asillustrated in FIGS. 1A and 1B, wireless devices 102, 104, 106 operatingat cell-edges, “hotspots,” and/or coverage “holes” of geographical areas148, 152 of DeNBs 110 and/or 112 may experience reduced channelcapacity, e.g., low Signal-to-Interference-Plus-Noise (“SINR”) levelsand/or Quality of Service (“QoS”) degradation. In one embodiment,wireless network 120 may instruct DeNBs 110 and/or 112 to selectrelay-capable wireless devices and/or mini-macros, for example, RN 108,operating within a radio range 150 of wireless devices 102, 104, 106 tofunction as a RN. DeNBs 110 and/or 112 may select RN 108 from multiplerelay-capable wireless devices and/or mini-macros based on, for example,collected Received Signal Strength Indicators (“RSSI”) and/or RadioFrequency (“RF”) parameters and establish an over-the-air link, forexample, interfaces 128, 130, with RN 108.

Once over-the-air links 128, 130 have been established (i.e., betweenDeNBs 110 and/or 112 and RN 108), DeNBs 110 and/or 112 can instructother wireless devices (e.g., clustered wireless devices 106,relay/non-relay capable wireless devices 102, 104, mini-macros, etc.)operating within radio range 150 of RN 108 to establish a radio accesslink, for example, interfaces 122, 124, with RN 108. That is, system 100may configure RN 108 via DeNBs 110 and/or 112 to function as an offloadAccess Point (“AP”) for wireless devices 102, 106 and/or other RNsoperating in the radio range 150 of RN 108; DeNBs 110 and/or 112 mayalso establish direct links 126 with wireless device 104 and/or otherRNs or wireless devices operating in the radio range 150 of RN 108and/or within geographical areas 148, 152 of DeNBs 110 and/or 112.

RNs are classified based on a number of protocol layers beingimplemented. For example, RN 108 may be configured as anAmplify-and-Forward (“AF”) relay, Decode-and-Forward (“DF”) relay, Layer3 relay, or can function as a mini-macro (e.g., a low-powered radioaccess node).

AF relays are classified as Layer 1 (“L1”) RNs, e.g., full duplex“repeaters” or “boosters,” which repeat by amplifying andre-transmitting a signal on a Physical (“PHY”) Layer of, for example, anOpen Systems Interconnection (“OSI”) Model. Because AF relays amplifyand re-transmit without decoding (e.g., amplification is carried out ona distorted signal) negative effects of, for example, radio hop, arealso amplified, which may deteriorate and/or constrain SINR levels andnetwork throughput. In addition, high processing time at DeNBs mayresult in Inter-Symbol Interference (“ISI”) at RNs and/or end-users.But, due to the mostly transparent nature of AF relays, and negligiblerelaying delay, AF relays are commonly used in simple coverage extensionscenarios.

DF relays are classified as Layer 2 (“L2”) RNs. DF relays incorporatethe functionalities of a Medium Access Control (“MAC”) Layer of, forexample, the OSI Model, and function as DeNBs, lacking only a fixedconnection (e.g., wired backhaul links) to the operator's core network,i.e., DF relays are self-backhauling. DF relays perform full signalreception and/or re-transmit procedures up to a Transmission ControlProtocol (“TCP”) Layer of, for example, the OSI Model, and use signalprocessing to decode and then re-generate useful signals including:error correction, re-modulation, and re-encoding. Because DF relaysignal processing introduces delay and/or complexity to the system,e.g., due to the modulation/de-modulation and/or encoding/re-encoding ofsignals, QoS for certain delay-sensitive traffic, for example,Voice-Over-IP (“VoIP”), may decrease. But, DF relays are extremelyuseful in interference-limited scenarios, for example, to enhancecell-edge performance.

L3 RNs include full Radio Resource Control (“RRC”) capabilities andinclude all of the protocol functionalities of DeNBs. For example, L3RNs can communicate with DeNBs through an x2-like interface, e.g.,similar to link 132 illustrated in FIG. 1A, or, when not configured as aRN, with DeNBs over a radio access link. L3 RNs can implement PacketData Convergence Protocols (“PDCP”) and/or Service Data Units (“SDUs”),etc., such that data packets at an Internet Protocol (“IP”) Layer of,for example, the OSI Model, are viewable at the RN. L3 RNs performde-modulation and de-coding of received RF signals (either uplink (“UL”)or downlink (“DL”)), process received data (e.g., by ciphering,combining/dividing, encoding, modulating, etc.), and re-transmit thedata to, for example, end-users. L3 RNs may be assigned a uniquePhysical Cell Identity (“PCP”) via the PHY Layer, which is differentfrom a PCI assigned to DeNBs.

RNs can also be classified based on a network resource usage strategy onthe over-the-air and radio access links. For example, RNs use ofspectrum may be classified as In-Band or Out-Band relaying. In oneembodiment, data packets related to applications running on wirelessdevices 102, 106 can be uploaded/downloaded from system 100 on UL and/orDL portions of over-the-air links 128, 130 and/or radio access links122, 124 via sub-layers of a User Plane (“UP”) protocol stack of, forexample, the OSI Model. For In-Band relaying, over-the-air links 128,130 and/or radio access links 122, 124 are operated on a same frequencycarrier. To avoid self-interference, over-the-air links 128, 130 and/orradio access links 122, 124 are time-multiplexed through reuse ofMultimedia-Broadcast-Over-Single-Frequency-Network (“MBSFN”) subframes.For Out-Band relaying, over-the-air links 128, 130 and/or radio accesslinks 122, 124 are operated on different carrier frequencies/spectrum.Out-Band relaying improves network capacity at the expense of largerspectrum demand for over-the-air links 128, 130.

Referring to FIGS. 1A-1E, RN 108 and/or wireless devices 102, 104, 106operating in geographical areas 148, 152 of DeNBs 110, 112 and/or radiorange 150 of RN 108 may continue to experience reduced channel capacity,e.g., low SINR levels, and/or QoS degradation due to, for example,limited backhaul capacity of DeNBs 110 and/or 112. In an exemplaryembodiment, system 100 may implement wireless technologies such asSU/MU-MIMO, OFDM, and/or advanced error correction techniques to achievethroughput gains.

As illustrated in FIGS. 1A and 1C-1E, system 100 can configure DeNBs 110and/or 112 to operate in SU/MU-MIMO Mode. For example, multipletransmit/receive (“Tx/Rx”) antennas 154, 154A, 154B, 166A, 166B, may bedeployed at DeNBs 110, 112, RN 108, and/or wireless devices 102, 104,106 such that signals on the Tx/Rx antennas (e.g., received at 156,156A, 156B, 168A, 168B) are “combined” using the same resources in bothfrequency and time, illustrated in FIG. 1E, to improve the Bit ErrorRate (“BER”) or data rate (e.g., bits/sec) for SU/MU-MIMO end-users. Toachieve throughput gains, DeNBs 110 and/or 112 may optimize networks'120 multipath conditions for SU/MU-MIMO by targeting rich scatteringconditions (i.e., where signals bounce around the environment ofgeographical areas 148, 152) and high SINR levels for multipath signals.In other words, DeNBs 110 and/or 112 operating in SU/MU-MIMO mode areconfigured to exploit multipath propagation by, for example, takingadvantage of random fading, multipath delay spread, etc.

In SU-MIMO mode, MIMO data streams are sent between DeNBs 110 and/or 112and a single wireless device 102 (i.e., point-to-point). For example, asillustrated in FIG. 1C, DeNB 110 may be configured to operate in SU-MIMOmode (e.g., transmit diversity, closed-loop SU-MIMO, open-loop SU-MIMO,and/or adaptive beamforming) to increase peak data rates (e.g., datarates over 300 Mbit/s) for wireless device users, for example, end-user102.

In MU-MIMO mode, separate data streams are sent to spatially separatedRNs and/or wireless devices over a same sub-channel, with each RN and/orwireless device serving as one of multiple Rx antennas. For example, asillustrated in FIG. 1D, MU-MIMO data streams may be transmitted betweenDeNB 110 and wireless devices 102, 104 using a same PRB (e.g., in bothfrequency and time, illustrated in FIG. 1E) to increase overall systemcapacity, though MU-MIMO does not increase throughput for individualRN's and/or wireless devices located in a geographical area of DeNBsover single-antenna techniques.

DeNBs 110 and/or 112 operating in SU/MU-MIMO mode may receiveinformation from RN 108 and/or wireless devices 102, 104, 106 including:(i) a Rank Indicator (“RI”), which indicates a number of layers (e.g.,data/spatial streams) that can be supported under current channelconditions and a modulation scheme; and, (ii) a Channel QualityIndicator (“CQI”), which indicates channel conditions under the currentoperating mode (e.g., SU/MU-MIMO mode), roughly corresponding to SINR.DeNBs 110 and/or 112 use CQI to select a correct Modulation and CodingScheme (“MCS”) for the indicated channel conditions. Combined with theMCS, CQI can be converted into an expected throughput, which is used byDeNBs 110 and/or 112 to adjust a current operating mode (e.g.,SU/MU-MIMO mode) and/or to allocate PRBs to RN 108 and/or wirelessdevices 102, 104, 106. For example, DeNBs 110 and/or 112 can allocatePRBs based on whether the CQI and RI reported by the RN 108 and/orwireless devices 102, 104, 106 match an expected value, and whethersignals on the Rx antennas are being received at an acceptable errorrate.

RNs 108 and/or wireless devices 102, 104, 106 may also analyze thechannel conditions of each Tx/Rx antenna, including multipathconditions. For example, RNs 108 and/or wireless devices 102, 104, 106can provide an RI and Precoding Matrix Indicator (“PMI”), whichdetermines an optimum precoding matrix for a current channel conditions,to DeNBs 110 and/or 112. Based on the RI and PMI, RNs 108 and/orwireless devices 102, 104, 106 can provide a CQI to DeNBs 110 and/or112, i.e., instead of basing CQI on the SU/MU-MIMO mode at DeNBs 110and/or 112. This enables DeNBs 110 and/or 112 to adapt datatransmissions based on channel conditions, for example, using memory160, scheduler 162, and/or pre-coding module 164.

Referring to FIGS. 1A and 1D, DeNBs 110 and/or 112 are configured tooperate in MU-MIMO mode. On the UL, RN 108 and/or wireless devices 102,104 are paired to share a same set of PRBs (e.g., in both frequency andtime, illustrated in FIG. 1E) for UL data streams to achieve throughputgains. Throughput gains are expected to be larger based on a highernumber of Rx antennas at DeNBs 110 and/or 112, for example, 4Rx, 8Rx,etc., may have higher gains than 2Rx.

Because MU-MIMO performance relies on good RN and/or wireless devicepairing and/or co-scheduling at DeNBs, pairing decisions are made at,for example, DeNBs 110 and/or 112 at every subframe, for example, everymillisecond. Primary criteria for RN 108 and/or wireless device 102,104, 106 pairing includes: (i) channel orthogonality (i.e.,non-overlapping and non-interfering channels) above a set threshold,which may be achieved by assigning cyclic shifts allocated to aDemodulation Reference Signal (“DM-RS”) to differentiate parallel datastreams received at DeNB 110; and, (ii) SINR above a set threshold.

Other secondary criteria for RN 108 and/or wireless device 102, 104pairing includes: (i) not pairing RNs and/or wireless devices if PRBs ina current TTI are enough to schedule the RNs and/or wireless deviceswithout pairing; (ii) configuring DeNBs to calculate an expected cellthroughput gain from pairing and if no throughput gain is determined,then the selected wireless devices are not paired; (iii) excludingHybrid-Automatic-Repeat-Requests (“HARQ”) re-transmission RNs and/orwireless devices from pairing; (iv) requiring a higher priority forNon-Giga Bit Rate (“Non-GBR”) RNs and/or wireless devices for pairing;(v) excluding RNs and/or wireless devices using TTI bundling frompairing; (vi) selecting high-speed RNs and/or wireless devices with lowpriority for pairing; and (vii) excluding TTI bundling RNs and/orwireless devices located at cell-edges of geographical areas of DeNBsfrom pairing.

Because DeNBs operating under a typical MU-MIMO mode prioritize usersfor MU-MIMO pairing primarily based on, for example, channelorthogonality and/or SINR, efficiencies for end-users, for example,wireless devices 102, 106 illustrated in FIG. 1A, of RNs chosen forMU-MIMO pairing may be reduced, decreasing overall cell-throughput.Given that RNs support multiple end-users, it is desirable to excludeusers from MU-MIMO pairing based on a “relay” status of the user toimprove average cell-throughput of the wireless network.

Communication system 100 includes wireless devices 102, 104, 106, RN108, DeNBs 110, 112, scheduler 114, controller node 116, gateway node118, and communication network 120. Other network elements may bepresent in the communication system 100 to facilitate communication, butare omitted for clarity, such as controller nodes, base stations, basestation controllers, gateways, mobile-switching centers, dispatchapplication processors, and location registers such as a Home LocationRegister (“HLR”) or Visitor Location Register (“VLR”). Furthermore,other network elements may be present to facilitate communicationbetween DeNBs 110, 112 and communication network 120, which are omittedfor clarity, including additional processing nodes, routers, gateways,and physical and/or wireless data links for carrying data among thevarious network elements.

Wireless devices 102, 104, 106 can be any device configured tocommunicate over system 100 using a wireless interface. For example,wireless devices 102, 104, 106 can include a Remote Terminal Unit(“RTU”), a cell phone, a smart phone, a computing platform such as alaptop, palmtop, or a tablet, a Personal Digital Assistant (“PDA”), oran internet access device, and combinations thereof. It is noted thatwhile three wireless devices are illustrated in FIGS. 1A-1D as being incommunication with one of RNs 108 and/or DeNBs 110, 112, any number ofwireless devices can be implemented according to various exemplaryembodiments disclosed herein.

The wireless interfaces of wireless devices 102, 104, 106 can include,for example, one or more transceivers for transmitting and receivingdata over communication system 100. Each transceiver can be associatedwith the same or different frequency bands, the same or different radioaccess technologies, the same or different network providers, and/or thesame or different services. For example, wireless devices 102, 104, 106can include a transceiver that is associated with one or more of thefollowing: Code Division Multiple Access (“CDMA”) 1×RTT, Global Systemfor Mobile communications (“GSM”), Worldwide Interoperability forMicrowave Access (“WiMAX”), Universal Mobile Telecommunications System(“UMTS”), Evolution Data Optimized (“EV-DO”), EV-DO rev. A, ThirdGeneration Partnership Project Long Term Evolution (“3GPP LTE”), and/orHigh-Speed Downlink Packet Access (“HSDPA”), IEEE 802.11, WirelessFidelity (“Wi-Fi”), Bluetooth, Zigbee, Infrared Data Association(“IrDA”), Multimedia Broadcast Multicast Service (“MBMS”), etc.

Wireless devices 102, 104, 106 can transmit and/or receive informationover communication system 100 using various communication services.These services can include various voice, data, and/or MBMS services andapplications. For example, mobile voice services, mobile data services,push-to-talk services, internet services, web browsing, email, pictures,picture messaging, video, video messaging, broadcast video, audio,voicemail, music, MP3's, ring tones, stock tickers, news alerts, etc.

RN 108 may be any relay-capable wireless device and/or mini-macro (e.g.,a low-powered radio access node, for example, a PICO node, FEMTO node,Remote Radio Head (“RRH”), etc.) capable of providing wirelesscommunications to other RNs and/or wireless devices 102, 104, 106 viaDeNBs 110, 112, and/or communication network 120 using a wired orwireless interface. RN 108 may be configured to connect to DeNBs 110and/or 112 via an In-Band/Out-Band over-the-air backhaul link 128, 130and/or a dedicated wired (e.g., Ethernet) or wireless (microwave)backhaul link. Links 128, 130 can comprise, RF, microwave, infrared, orother similar signal, and can use a suitable protocol, for example, CDMA1×RTT, GSM, WiMAX, UMTS, EV-DO, EV-DO rev. A, 3GPP LTE, HSDPA, IEEE802.11, Wi-Fi, IrDA, or combinations thereof. Although one RN 108 isillustrated in FIGS. 1A and 1B as being in communication with DeNBs 110and/or 112, any number of RNs can be implemented according to variousexemplary embodiments disclosed herein.

DeNBs 110 and 112 can be any network node capable of providing wirelesscommunications to RN 108 and/or wireless devices 102, 104, 106 and canbe, for example, a Base Transceiver Station (“BTS”), a radio basestation, an eNodeB device, or an enhanced eNodeB device. DeNBs 110 and112 can include a scheduler module 162, illustrated in FIGS. 1B-1D, orcan be in communication with scheduler node 114, illustrated in FIG. 1A.DeNBs 110 and 112 can use scheduler module 162 and/or scheduler node 114to allocate resources (e.g., the next available PRB, wireless spectrum,etc.) to RN 108 and/or wireless devices 102, 104, 106. Scheduler module162 and/or scheduler node 114 can collect and store capacity andtransmission delay characteristics (e.g., buffered data, signal quality,throughput, GBR/Non-GBR, busy hour, backhaul capacity, mobility, etc.)reported by RN 108 and/or wireless devices 102, 104, 106 at DeNBs 110and/or 112 and can distribute resources via a scheduling algorithm to RN108 and/or wireless devices 102, 104, 106 based on the collectedcharacteristics, “relay” status, and/or an operating mode (e.g.,SU/MU-MIMO) of DeNBs 110 and/or 112.

DeNBs 110, 112 and RN 108 can comprise processors 158, 170A, 170B andassociated circuitry to execute or direct the execution ofcomputer-readable instructions to obtain information. DeNBs 110, 112 andRN 108 can retrieve and execute software from storage 160, 172A, 172B,which can include a disk drive, a flash drive, memory circuitry, or someother memory device, and which can be local or remotely accessible. Thesoftware comprises computer programs, firmware, or some other form ofmachine-readable instructions, and may include an operating system,utilities, drivers, network interfaces, applications, or some other typeof software, including combinations thereof. DeNBs 110, 112 and RN 108can receive instructions and other input at a user interface. Althoughonly DeNBs 110, 112 and RN 108 are illustrated in FIGS. 1A-1D, RN 108and wireless devices 102, 104, 106 can be in communication with aplurality of DeNBs. The plurality of DeNBs can be associated withdifferent networks and can support different communication protocols andradio access technologies.

Controller node 116 can be any network node configured to communicateinformation and/or control information over communication system 100.Controller node 116 can be a standalone computing device, computingsystem, or network component, and can be accessible, for example, by awired or wireless connection, or through an indirect connection such asthrough a computer network or communication network. For example,controller node 116 can include a Mobility Management Entity (“MME”), aHome Subscriber Server (“HSS”), a Policy Control and Charging RulesFunction (“PCRF”), an Authentication, Authorization, and Accounting(“AAA”) node, a Rights Management Server (“RMS”), a SubscriberProvisioning Server (“SPS”), a policy server, etc. One of ordinary skillin the art would recognize that controller node 116 is not limited toany specific technology architecture, such as LTE, and can be used withany network architecture and/or protocol.

Controller node 116 can comprise a processor and associated circuitry toexecute or direct the execution of computer-readable instructions toobtain information. Controller node 116 can retrieve and executesoftware from storage, which can include a disk drive, a flash drive,memory circuitry, or some other memory device, and which can be local orremotely accessible. The software comprises computer programs, firmware,or some other form of machine-readable instructions, and may include anoperating system, utilities, drivers' network interfaces, applications,or some other type of software, including combinations thereof.Controller node 116 can receive instructions and other input at a userinterface.

Gateway node 118 can be any network node configured to interface withother network nodes using various protocols that communicate, route, andforward communication data addressed to DeNBs 110, 112, RN 108, and/orwireless devices 102, 104, 106. In addition, gateway node 118 can act asa mobility anchor for RN 108 and/or wireless devices 102, 104, 106during handovers between different frequencies and/or different radioaccess technologies supported by the same access node. Gateway node 118can be a standalone computing device, computing system, or networkcomponent, and can be accessible, for example, by a wired or wirelessconnection, or through an indirect connection such as through a computernetwork or communication network. For example, gateway node 118 caninclude a Serving Gateway (“SGW”) and/or Public Data Network Gateway(“PGW”), etc. One of ordinary skill in the art would recognize thatgateway node 118 is not limited to any specific technology architecture,such as LTE, and can be used with any network architecture and/orprotocol.

Gateway node 118 can comprise a processor and associated circuitry toexecute or direct the execution of computer-readable instructions toobtain information. Gateway node 118 can retrieve and execute softwarefrom storage, which can include a disk drive, a flash drive, memorycircuitry, or some other memory device, and which can be local orremotely accessible. The software comprises computer programs, firmware,or some other form of machine readable instructions, and may include anoperating system, utilities, drivers, network interfaces, applications,or some other type of software, including combinations thereof. Gatewaynode 114 can receive instructions and other input at a user interface.

Communication links 122, 124, 126, 128, 130, 132, 134, 136, 138, 140,142, 144, 146 can be wired or wireless communication links and usevarious communication protocols such as Internet, Internet Protocol(“IP”), LAN, optical networking, Hybrid Fiber Coax (“HFC”), telephony,T1, or some other communication format—including combinations,improvements, or variations thereof. Wireless communication links 122,124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146 can comprise,for example, RF, microwave, infrared, or other similar signal, and canuse a suitable communication protocol, for example, CDMA 1×RTT, GSM,WiMAX, UMTS, EV-DO, EV-DO rev. A, 3GPP LTE, HSDPA, IEEE 802.11, Wi-Fi,IrDA, or combinations thereof. Communication links 122, 124, 126, 128,130, 132, 134, 136, 138, 140, 142, 144, 146 can be a direct link ormight include various equipment, intermediate components, systems, andnetworks.

Wireless communication links 122, 124, 126, 128, 130, 132, 134, 136,138, 140, 142, 144, 146 can comprise one or more logical channels, oneor more transport channels, and one or more physical channels. A logicalchannel typically describes different flows of information, such asbearer data and/or signaling information, and can be organizeddifferently for UL and DL portions of communication links 122, 124, 126,128, 130, 132, 134, 136, 138, 140, 142, 144, 146. A transport channelcan organize information, such as data packets, received from one ormore logical channels for transmission over communication links 122,124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, and candefine how and with what type of characteristics information istransferred by the physical channel. A physical channel can comprise,for example, a carrier frequency or a number of carrier frequencies in acommunication link 122, 124, 126, 128, 130, 132, 134, 136, 138, 140,142, 144, 146, and can provide a physical transmission medium for one ormore transport channels.

Communication network 120 can be a wired and/or wireless communicationnetwork, and can comprise processing nodes, routers, gateways, andphysical and/or wireless data links for carrying data among variousnetwork elements, including combinations thereof, and can include a LAN,a WAN, and an internetwork (including the Internet). Communicationnetwork 120 can be capable of carrying data, for example, to supportvoice, push-to-talk, broadcast video, and data communications by awireless device, such as, for example, wireless devices 102, 104, 106.Wireless network protocols can comprise CDMA 1×RTT, GSM, WiMAX, UMTS,EV-DO, EV-DO rev. A, 3GPP LTE, HSDPA, IEEE 802.11, Wi-Fi, IrDA, andcombinations thereof. Wired network protocols that may be utilized bycommunication network 120 comprise Ethernet, Fast Ethernet, GigabitEthernet, Local Talk (such as Carrier Sense Multiple Access withCollision Avoidance), Token Ring, Fiber Distributed Data Interface(“FDDI”), and Asynchronous Transfer Mode (“ATM”). Communication network120 may also comprise additional base stations, controller nodes,telephony switches, internet routers, network gateways, computersystems, communication links, or some other type of communicationequipment, and combinations thereof.

FIG. 2 illustrates an exemplary illustrates an exemplary method forexcluding RNs from MU-MIMO pairing. The method will be discussed withreference to aspects of the exemplary communication system 100illustrated in FIGS. 1A-1E. However, the method can be implemented withany suitable communication. In addition, although FIG. 2 depicts stepsperformed in a particular order for purposes of illustration anddiscussion, the method discussed herein is not limited to any particularorder or arrangement. One skilled in the art, using the disclosuresprovided herein, will appreciate that various steps of the method can beomitted, rearranged, combined and/or adapted in various ways.

Referring to FIG. 2, at step 202, a relay-capable status of wirelessdevices and/or mini-macros located in a geographic area of an accessnode is determined. For example, as illustrated in FIGS. 1A and 1B,wireless devices 102, 104, 106 operating at cell-edges, “hotspots,”and/or coverage “holes” of geographical areas 148, 152 of DeNBs 110, 112may experience reduced channel capacity, e.g., low SINR levels and/orQoS degradation. Wireless network 120 may instruct DeNBs 110 and/or 112to select relay-capable wireless devices and/or mini-macros operatingwithin geographical areas 148, 152 and/or a radio range of wirelessdevices 102, 104, 106 to function as a RN, for example, RN 108. DeNBs110 and/or 112 may select RN 108 from multiple relay-capable wirelessdevices and/or mini-macros based on, for example, collected RSSI and/orRF parameters reported by the relay-capable wireless devices and/ormini-macros at DeNBs 110 and/or 112.

Once RN 108 has been selected, DeNBs 110 and/or 112 may perform anattach procedure. For example, an RRC Connection setup may be performedbetween RN 108 and DeNBs 110 and/or 112. RN 108 may transmit a RNcapability indicator (e.g., which indicates a relay-capable “status” ofRN 108) to DeNBs 110 and/or 112 during the RRC Connection establishment.Based on the RN capability indicator, DeNBs 110 and/or 112 may establishan interface, for example, an S1 interface, with controller node 116 forsignaling support of RN 108. If controller node 116 is capable ofsupporting RN 108, controller node 116 may transmit an RN supportmessage to DeNBs 110 and/or 112 during the S1 interface setup andimplement an Operations, Administration, and Management (“OAM”) protocolto complete RN configuration. After configuration, DeNBs 110 and/or 112may initiate setup of bearers (e.g., S1/x2/Un bearers) for RN 108 and RN108 may initiate setup of interfaces (e.g., S1, x2, Un, Uu interfaces)with DeNBs 110 and/or 112. DeNBs 110 and/or 112 may also initiate an RNreconfiguration procedure via RRC signaling for RN-specific parameters.After the RN reconfiguration update procedure is performed, DeNBs 110and/or 112 can update the PCI of RN 108 and instruct wireless devices102, 106 within a radio range 150 of RN 108 to communicate over thenetwork 120 via RN 108. For example, DeNBs 110 and/or 112 may perform ahandover of wireless devices 102, 106 from DeNBs 110 and/or 112 to RN108.

At step 204, relay-capable wireless devices and/or RNs are excluded forMU-MIMO pairing. In one embodiment, DeNBs 110 and/or 112 may beconfigured to operate in SU/MU-MIMO mode. Multiple Tx/Rx antennas aredeployed at DeNBs 110, 112, RN 108, and/or wireless devices 102, 104,106 such that signals on the Tx/Rx may be combined using a same PRB(e.g., in both frequency and time, as illustrated in FIG. 1E) to improvethe BER or data rate (e.g., bits/sec) for SU/MU-MIMO end-users.

For example, DeNBs 110 and/or 112 operating in SU/MU-MIMO mode mayreceive information from RN 108 and/or wireless devices 102, 104, 106located in geographic areas 148, 152 including: (i) RI, which indicatesa number of layers (e.g., data/spatial streams) that can be supportedunder current channel conditions and a modulation scheme; and, (ii) aCQI, which indicates channel conditions under SU/MU-MIMO operating mode,roughly corresponding to SINR. Based on the CQI's collected from RN 108and/or wireless devices 102, 104, 106, DeNBs 110 and/or 112 select acorrect MCS for the channel conditions. Combined with the MCS, CQI canbe converted into an expected throughput, which is used by DeNBs 110and/or 112 to adjust a current operating mode (e.g., SU/MU-MIMO mode)and an amount of PRBs allocated to RNs 108 and/or wireless devices 102,104, 106.

RN 108 and/or wireless devices 102, 104, 106 may also analyze channelconditions and provide an RI and PMI to DeNBs 110 and/or 112. Based onthe RI and PMI, RN 108 and/or wireless devices 102, 104, 106 can providea CQI to DeNBs 110 and/or 112, i.e., instead of basing CQI on theSU/MU-MIMO operating mode at DeNBs 110 and/or 112. This enables DeNBs110 and/or 112 to adapt data transmissions based on channel conditions,for example, using memory 160, packet schedulers 114, 162, and/orpre-coding module 164.

In an exemplary embodiment, packet schedulers 114, 162 for DeNBs 110and/or 112 operating in SU/MU-MIMO mode can be carried out in twophases: time domain packet scheduler (“TDPS”) and frequency domainpacket scheduler (“FDPS”), as illustrated in FIG. 1E. RN 108 and/orwireless devices 102, 104, 106 are scheduled in SU/MU-MIMO mode basedon, for example, MU-MIMO pairing criteria being met.

For pairing purposes, RN 108 and/or wireless devices 102, 104, 106 areclassified into primary (i.e., RNs and/or wireless devices scheduled fortransmission using a same SU-MIMO TD-FD PS scheme) and candidate (i.e.,MU-MIMO candidate RNs and/or wireless devices) RNs and/or wirelessdevices. For each PRB, DeNBs 110 and/or 112 may select from the list ofMU-MIMO candidates a best RN and/or wireless device to pair with aselect primary RN and/or wireless devices. Because MU-MIMO performancerelies on good RN and/or wireless device pairing and/or co-scheduling atDeNBs, pairing decisions are made at DeNBs 110 and/or 112 at everysubframe, for example, every millisecond.

Typically, the primary criteria for RNs 108 and/or wireless devices 102,104, 106 pairing includes: (i) channel orthogonality (i.e.,non-overlapping and non-interfering channels) above a set threshold,which may be achieved by assigning cyclic shifts allocated to, forexample, a Demodulation Reference Signal (“DM-RS”) to differentiateparallel data streams received at DeNBs 110 and/or 112; and, (ii) SINRabove a set threshold.

For example, candidate RNs and/or wireless devices should have anassigned Precoder that is orthogonal to the selected primary RN and/orwireless devices. In an exemplary embodiment, DL transmission schemes ofDeNBs 110 and/or 112 may be supported at a PHY layer of the OSI Model bya set of DL reference signals. These reference signals can be specificto RN 108 and/or wireless devices 102, 104, 106, i.e., DM-RS, orspecific to geographical areas 148, 152 of DeNBs 110 and/or 112, i.e.,Common Reference Signals (“CRS”). DM-RS' are pre-coded signals used fordemodulation purposes on scheduled PRBs. For example, pre-coding module164 of DeNBs 110 and/or 112 may apply pre-coding to data transmissionstargeted to RN 108 and/or wireless devices 102, 104, 106 based onchannel feedback received from RN 108 and/or wireless devices 102, 104,106, including RI, CQI, and PMI. CRS' are not pre-coded signals and areused by RNs 108 and/or wireless devices 102, 104, 106 for channelestimation.

To fully exploit MU-MIMO mode, data/spatial streams intended to/fromDeNBs 110 and/or 112 to/from RN 108 and/or wireless devices 102, 104,106 need to be well separated and orthogonal at both Tx/Rx sides.Optimal pre-coding for MU-MIMO mode at, for example, pre-coding module164 of DeNBs 110 and/or 112, may include Dirty Paper Coding (“DPC”)combined with user scheduling (e.g., from schedulers 114 and/or 164) andpower loading. Additional pre-coding techniques may include ChannelInversion (“CI”), e.g., to cancel interference, and/or RegularizedChannel Inversion (“RCI”), e.g., to attenuate interference. To avoidscheduling RNs 108 and/or wireless devices 102, 104, 106 located at, forexample, a cell-edge of DeNBs 110 and/or 112, into MU-MIMO mode, apredicted SINR of both the primary and candidate RNs 108 and/or wirelessdevices 102, 104, 106 at the considered PRB are compared to the setthreshold.

Generally, in addition to channel orthogonality and SINR, othersecondary criteria are used for RN and/or wireless device MU-MIMOpairing, including: (i) not pairing RNs and/or wireless devices if PRBsin a current TTI are enough to schedule RNs and/or wireless deviceswithout pairing; (ii) configuring DeNBs to calculate an expected cellthroughput gain from pairing and, if no throughput gain is determined,then the selected wireless devices are not paired; (iii) excluding HARQre-transmission RNs and/or wireless devices from pairing; (iv) requiringa higher priority for Non-GBR RNs and/or wireless devices for pairing;(v) excluding RNs and/or wireless devices using TTI bundling frompairing; (vi) selecting high-speed RNs and/or wireless devices with lowpriority for pairing; and (vii) excluding TTI bundling RNs and/orwireless devices located at cell-edges of geographical areas frompairing.

In an exemplary embodiment, DeNBs 110 and/or 112 may generate a list ofRNs 108 and/or wireless devices 102, 104, 106 that meet the primaryand/or secondary criterion and store the candidate list at, for example,memory module 160 of DeNBs 110 and/or 112. Typically, candidate RNsand/or wireless devices from the list that have a highest metric (e.g.,based on the primary and secondary criterion) in MU-MIMO mode areselected for pairing with the primary RN and/or wireless devices and areset to MU-MIMO transmission mode. If none of the candidate RNs and/orwireless devices meet the primary and/or secondary criterion, theprimary RN and/or wireless devices will transmit in SU-MIMO mode.

Because DeNBs 110 and/or 112 operating under a typical MU-MIMO modeprioritize users i.e., RN 108 and/or wireless devices 102, 104, 106, forMU-MIMO pairing primarily based on, for example, channel orthogonalityand/or SINR, efficiencies for end-users of RNs chosen for MU-MIMOpairing may be reduced, decreasing overall cell-throughput. Given thatRNs support multiple end-users, it is desirable to exclude users forMU-MIMO pairing based on a “relay” status of the user, that is,relay-capable wireless devices (including mini-macros) and/or RNs, toimprove average cell-throughput of the wireless network. Averagecell-throughput may be improved, in part, by transmitting data packetsto relay-capable wireless devices (including mini-macros) and/or RNsusing SU-MIMO.

At step 206, resources are allocated to non-relay-capable wirelessdevices (including mini-macros) paired for MU-MIMO transmissions basedon priority. For example, scheduler 114 and/or scheduler module 162 ofDeNBs 110 and/or 112 may allocate resources (e.g., the next availablePRB, wireless spectrum, etc.) to non-relay-capable wireless devicespaired for MU-MIMO transmissions based on, for example, capacity andtransmission delay characteristics reported at DeNBs 110 and/or 112 andcan distribute resources via a scheduling algorithm (e.g., proportionalfairness, round robin, etc.). The scheduling algorithms may prioritizeresource allocation based on the collected characteristics, “relay”status, and/or an operating mode, i.e., SU/MU-MIMO mode, of DeNBs 110,112, RN 108, and wireless devices 102, 104, 106.

FIG. 3 illustrates a portion 300 of the exemplary communication system100 illustrated in FIGS. 1A-1E for excluding RNs for MU-MIMO pairing.FIG. 3 will be discussed with reference to aspects of the exemplarycommunication system 100 illustrated in FIGS. 1A-1E.

In operation, RNs may be exploited at cell-edges, “hotspots,” and/orcoverage “holes” of geographical areas of high-powered, large scaleaccess nodes, for example, DeNB 310, to boost spatial coverage and/orcell-edge capacity. RN 312 may be configured to serve a plurality ofend-users 301, 306 via In-Band and/or Out-Band over-the-air interfaces330 to DeNB 310 and can be classified based on a number of protocollayers being implemented, as discussed in reference to FIGS. 1A-1D. Forexample, RN 312 may be configured as an AF relay, DF relay, and/or L3relay. DeNB 310 may also establish direct links 326 with wirelessdevices 302, 304, 305 and/or other RNs operating in a radio range of RN312 and/or within a geographical area of DeNB 310.

As illustrated in FIG. 3, DeNBs 310 can be configured to operate inSU/MU-MIMO Mode. For example, multiple Tx/Rx antennas may be deployed atDeNB 310, RN 312, and/or wireless devices 301, 302, 304, 305, 306 suchthat signals on the Tx/Rx may be combined using a same PRB (e.g., inboth frequency and time, as illustrated in FIG. 1E) to improve the BERor data rate (e.g., bits/sec) for SU/MU-MIMO end-users. DeNB 310 canreceive information from RN 312 and/or wireless devices 301, 302, 304,305, 306 located in geographic areas of DeNB 310 including RI and CQI.Based on the CQI's collected from RN 312 and/or wireless devices 301,302, 304, 305, 306, DeNB 310 can select a correct MCS for the channelconditions. Combined with the MCS, CQI can be converted into, forexample, an expected throughput. DeNB 310 can use this information toadjust its current operating mode (e.g., SU/MU-MIMO mode) and an amountof PRBs allocated to RN 312 and/or wireless devices 301, 302, 304, 305,306. RN 312 and/or wireless devices 301, 302, 304, 305, 306 may alsoanalyze channel conditions and provide an RI and PMI to DeNB 310. Basedon the RI and PMI, RN 312 and/or wireless devices 301, 302, 304, 305,306 can provide a CQI to DeNB 310 instead of basing CQI on theSU/MU-MIMO operating mode at DeNB 310. This enables DeNB 310 to adaptdata transmissions based on channel conditions, for example, usingmemory, packet schedulers, and/or pre-coding modules as discussed withreference to FIGS. 1B-1D.

RN 312 and/or wireless devices 301, 302, 304, 305, 306 are scheduled inSU/MU-MIMO mode based on, for example, MU-MIMO pairing criteria beingmet. For example, RN 312 and/or wireless devices 301, 302, 304, 305, 306are classified into primary and candidate RN 308 and/or wireless devices301, 304, 305, 306. For each PRB, DeNB 310 may select from the list ofMU-MIMO candidates a best RN and/or wireless device to pair with primaryRN and/or a primary wireless device 302. Because MU-MIMO performancerelies on good RNs and/or wireless device pairing and/or co-schedulingat DeNBs, pairing decisions are made at DeNB 310 at every subframe, forexample, every millisecond.

In an exemplary embodiment, DeNB 310 may exclude relay-capable wirelessdevices 305 and/or RN 312 for MU-MIMO pairing and transmit resources(e.g., the next available PRB and/or wireless spectrum) to excludedrelay-capable wireless devices 305 and/or RN 312 using SU-MIMO.Non-relay-capable wireless devices, for example, wireless device 304,may be selected from the candidate list based on channel orthogonalityand SINR meeting a set threshold. Wireless device 304 may be paired withnon-relay-capable wireless device 302 for MU-MIMO transmissions.Scheduler 114, illustrated in FIG. 1A, and/or a scheduler module (notshown) of DeNB 310 may allocate resources (e.g., the next available PRB,wireless spectrum, etc.) to relay-capable wireless devices 305 and/or RN312 using SU-MIMO based on, for example, capacity and transmission delaycharacteristics reported at DeNB 310 and can distribute resources via ascheduling algorithm. Scheduler 114 and/or a scheduler module (notshown) of DeNB 310 may allocate resources (e.g., the next available PRB,wireless spectrum, etc.) to paired non-relay-capable wireless devices302, 304 using MU-MIMO based on, for example, channel orthogonality,SINR, and other secondary criterion and can distribute resources via ascheduling algorithm.

FIG. 4 illustrates another exemplary method for excluding RNs forMU-MIMO pairing. The method will be discussed with reference to aspectsof the exemplary communication system 100 illustrated in FIGS. 1A-1E,and the portion 300 of the exemplary communication system 100illustrated in FIG. 3. In addition, although FIG. 4 depicts stepsperformed in a particular order for purposes of illustration anddiscussion, the method discussed herein is not limited to any particulararrangement. One skilled in the art, using the disclosures providedherein, will appreciate that various steps of the method can be omitted,rearranged, combined and/or adapted in various ways.

Referring to FIG. 4, at steps 402 and 404, a relay “status” of wirelessdevices operating in a geographic area of DeNBs operating in SU/MU-MIMOmode is determined; at least one relay-capable wireless device(including relay-capable mini-macros) is selected to function as a RN.Referring to FIG. 3, wireless devices 301, 306 operating at cell-edges,“hotspots,” and/or coverage “holes” of a geographical area (not shown)of DeNB 310 may experience reduced channel capacity, e.g., low SINRlevels and/or QoS degradation. DeNB 310 may select a relay-capablewireless device and/or mini-macros operating within the geographicalarea to function as a RN, for example, RN 312. DeNB 310 may select RN312 from multiple relay-capable wireless devices based on collected RSSIand/or RF parameters reported at DeNBs 310 by, for example, RNs 312and/or wireless device 305.

Once RN 312 has been selected, DeNB 310 may perform an attach procedure.For example, an RRC Connection setup may be performed between RN 312 andDeNB 310. RN 312 may transmit a RN capability indicator (e.g., whichindicates a relay-capable “status” of RN 312) to DeNB 310 during the RRCConnection establishment. Based on the RN capability indicators, DeNBs310 may establish interfaces, for example, S1 interfaces, withcontroller node 116, illustrated in FIG. 1A, for signaling support of RN312. If controller node 116 is capable of supporting RN 312, controllernode 116 may transmit a RN support message to DeNB 310 during the S1interface setup and implement an OAM protocol to complete RNconfiguration. After configuration, DeNB 310 may initiate setup ofbearers (e.g., S1/x2/Un bearers) for RN 312 and RN 312 may initiatesetup of interfaces (e.g., S1, x2, Un, Uu interfaces) with DeNB 310.DeNB 310 may also initiate an RN reconfiguration procedure via RRCsignaling for RN-specific parameters.

At step 406, DeNB 310 can instruct wireless devices located in a radiorange of the selected RN to communicate with the communication networkvia the RN. For example, after the RN reconfiguration update procedureat step 404 is performed, DeNB 310 can update the PCI of RN 312 andinstruct, for example, wireless devices 301, 306 operating within aradio range (not shown) of RN 312 to communicate over system 100,illustrated in FIG. 1A, via RN 312. For example, DeNB 310 may perform ahandover of wireless devices 301, 306 from DeNB 310 to RN 312.

At step 408, DeNB 310 may exclude relay-capable wireless devices(including mini-macros) and/or RNs from MU-MIMO pairing. For example,DeNB 310 may be configured to detect a relay-connection between RN 312and DeNB 310 and/or a relay-capability between relay-capable wirelessdevice 305 and DeNB 310 based on a unique PLMN. DeNB 310 may exclude thedetected relay-capable wireless devices 305 and/or RN 312 from MU-MIMOpairing and configure relay-capable wireless devices 305 and/or RN 312for SU-MIMO mode.

At step 410, a channel orthogonality of non-relay-capable wirelessdevices (including mini-macros) located in a geographic area of anaccess node is determined. For example, DeNB 310 operating in SU/MU-MIMOmode may receive information from RN 312 and relay-capable wirelessdevices 305 (excluded from MU-MIMO pairing) and non-relay capablewireless devices 301, 302, 304, 306 located in a geographic area (notshown) of DeNB 310 including: RI and CQI. Based on the collected CQI's,DeNB 310 may select a correct MCS for the channel conditions. Combinedwith the MCS, CQI can be converted into, for example, an expectedthroughput. DeNB 310 may use this information to determine whether ornot to implement SU/MU-MIMO mode and an amount of PRBs to allocate to RN312, relay-capable wireless device 305, and/or wireless devices 301,302, 304, 306. RN 312, relay-capable wireless device 305, and/orwireless devices 301, 302, 304, 306 may also analyze channel conditionsand provide RI and PMI to DeNB 310. Based on the RI and PMI, RN 312,relay-capable wireless device 305, and/or wireless devices 301, 302,304, 306 can provide a CQI to DeNB 310, i.e., instead of basing CQI onthe SU/MU-MIMO operating mode at DeNB 310.

In an exemplary embodiment, non-relay-capable wireless device 304 isassigned a Precoder that is orthogonal to primary non-relay-capablewireless device 302. For example, DeNB 310 can pre-code referencesignals, i.e., DM-RS, specific to non-relay-capable wireless device 304for demodulation purposes on scheduled PRBs; DeNB 310 applies thepre-coding based on channel feedback received from non-relay-capablewireless device 304 including RI, CQI, and PMI. Optimal pre-coding forMU-MIMO mode at DeNB 310 may include DPC, user-scheduling, and powerloading. Additional pre-coding techniques can include CI and/or RCI.Based on the channel orthogonality, DeNB 310 can generate a list ofnon-relay-capable wireless devices located in the geographic area (notshown) of DeNB 310 for pairing with primary non-relay-capable wirelessdevice 302. The generated list may be stored at, for example, a memorymodule (not shown) or at storage 508 of processing node 500 illustratedin FIG. 5.

At step 412, non-relay-capable wireless devices whose determined channelorthogonality and SINR meets a set threshold are selected for MU-MIMOpairing. For MU-MIMO pairing, non-relay capable wireless devices 302 and304 are scheduled for MU-MIMO pairing based on MU-MIMO pairing criteriabeing met. In an exemplary embodiment, wireless device 302 is classifiedas a primary wireless device (i.e., a wireless device scheduled fortransmission using an SU-MIMO TD-FD PS scheme) and wireless device 304is classified as a candidate (i.e., MU-MIMIO candidate). For each PRB,DeNB 310 selects from the list of candidates (e.g., non-relay-capablewireless device 301, 304, 306) a best candidate to pair with primarywireless device 302. For example, DeNB 310 may select any of wirelessdevices 301, 304, 306 for MU-MIMO pairing with primary wireless device302 based on a channel orthogonality and SINR meeting a set threshold.

In other words, non-relay-capable wireless devices are prioritized overRNs for MU-MIMO pairing based on channel orthogonality and SINR. Forexample, DeNB 310 may prioritize wireless device 304 for pairing withprimary wireless device 302 over relay-capable wireless device 305and/or RN 312 based on a candidate having a highest metric (e.g., ametric based on a non-relay-capable status, channel orthogonality, SINR,or other secondary criterion). The secondary criterion may include: (i)not pairing RNs and/or relay-capable wireless devices if PRBs in acurrent TTI are enough to schedule RNs and/or relay-capable wirelessdevices without pairing; (ii) configure DeNB to calculate an expectedcell throughput gain from pairing and, if no throughput gain isdetermined, then the selected relay-capable wireless devices and/or RNsare not paired; (iii) excluding HARQ re-transmission RNs and/orrelay-capable wireless devices from pairing; (iv) requiring a higherpriority for Non-GBR RNs and/or relay-capable wireless devices forpairing; (v) excluding RNs and/or relay-capable wireless devices usingTTI bundling from pairing; (vi) selecting high-speed RNs and/orrelay-capable wireless devices with low priority for pairing; and (vii)excluding TTI bundling RNs and/or relay-capable wireless devices locatedat cell-edges from pairing. If none of candidate non-relay capablewireless devices 301, 304, 306 meet the primary and/or secondarycriterion, the primary non-relay-capable wireless device 302 maytransmit in SU-MIMO mode. Alternatively, primary non-relay-capablewireless device 302 may be paired for MU-MIMO with, for example, a relaycapable wireless device (including mini-macros) 305 or RN 312 based onchannel orthogonality.

At step 414, resources are allocated to non-relay-capable wirelessdevices paired for MU-MIMO transmissions based on priority. For example,scheduler 114, illustrated in FIG. 1A, and/or a scheduler module (notshown) of DeNB 310 may allocate resources (e.g., the next available PRB,wireless spectrum, etc.) to MU-MIMO paired wireless devices 302, 304and/or relay-capable wireless devices 305 and RN 312 using SU-MIMO modebased on, for example, capacity and transmission delay characteristicsreported at DeNB 310. Resources may be distributed via a schedulingalgorithm (e.g., proportional fairness, round robin, etc.). Thescheduling algorithms may prioritize resource allocation based on thecollected characteristics, “relay” status, and/or operating mode, i.e.,SU/MU-MIMO mode, of DeNB 310, RN 312, relay-capable wireless device 305,and/or non-relay capable wireless devices 301, 302, 304, 306.

FIG. 5 illustrates an exemplary processing node 500 in a communicationsystem. Processing node 500 comprises communication interface 502, userinterface 504, and processing system 506 in communication withcommunication interface 502 and user interface 504. Processing node 500can be configured to determine a communication access node for awireless device. Processing system 506 includes storage 508, which cancomprise a disk drive, flash drive, memory circuitry, or other memorydevice. Storage 508 can store software 510 which is used in theoperation of the processing node 500. Storage 508 may include a diskdrive, flash drive, data storage circuitry, or some other memoryapparatus. Software 510 may include computer programs, firmware, or someother form of machine-readable instructions, including an operatingsystem, utilities, drivers, network interfaces, applications, or someother type of software. Processing system 506 may include amicroprocessor and other circuitry to retrieve and execute software 510from storage 508. Processing node 500 may further include othercomponents such as a power management unit, a control interface unit,etc., which are omitted for clarity. Communication interface 502 permitsprocessing node 500 to communicate with other network elements. Userinterface 504 permits the configuration and control of the operation ofprocessing node 500.

Examples of processing node 500 include DeNBs 110, 112, 310, RNs 108,312, scheduler 114, controller nodes 116, and gateway node 118.Processing node 500 can also be an adjunct or component of a networkelement, such as an element of DeNBs 110, 112, 310, RNs 108, 312,schedulers modules/nodes 114, controller node 116, and gateway node 118.Processing node 500 can also be another network element in acommunication system. Further, the functionality of processing node 500can be distributed over two or more network elements of a communicationsystem.

The exemplary systems and methods described herein can be performedunder the control of a processing system executing computer-readablecodes embodied on a computer-readable recording medium or communicationsignals transmitted through a transitory medium. The computer-readablerecording medium is any data storage device that can store data readableby a processing system, and includes both volatile and nonvolatilemedia, removable and non-removable media, and contemplates mediareadable by a database, a computer, and various other network devices.

Examples of the computer-readable recording medium include, but are notlimited to, read-only memory (ROM), random-access memory (RAM), erasableelectrically programmable ROM (EEPROM), flash memory or other memorytechnology, holographic media or other optical disc storage, magneticstorage including magnetic tape and magnetic disk, and solid statestorage devices. The computer-readable recording medium can also bedistributed over network-coupled computer systems so that thecomputer-readable code is stored and executed in a distributed fashion.The communication signals transmitted through a transitory medium mayinclude, for example, modulated signals transmitted through wired orwireless transmission paths.

The above description and associated figures teach the best mode of theinvention. The following claims specify the scope of the invention. Notethat some aspects of the best mode may not fall within the scope of theinvention as specified by the claims. Those skilled in the art willappreciate that the features described above can be combined in variousways to form multiple variations of the invention, and that variousmodifications may be made to the configuration and methodology of theexemplary embodiments disclosed herein without departing from the scopeof the present teachings. Those skilled in the art also will appreciatethat various features disclosed with respect to one exemplary embodimentherein may be used in combination with other exemplary embodiments withappropriate modifications, even if such combinations are not explicitlydisclosed herein. As a result, the invention is not limited to thespecific embodiments described above, but only by the following claimsand their equivalents.

What is claimed is:
 1. A method for enabling Multi-UserMultiple-Input-Multiple-Output (MU-MIMO) pairing of wireless devicesserved by an access node, the method comprising: determining a channelorthogonality and Signal-to-Interference-Plus-Noise Ratio (SINR) of aplurality of wireless devices located in a geographic area served by theaccess node; excluding relay nodes located in the geographic area fromMU-MIMO pairing, wherein excluding the relay nodes comprises detecting arelay node capability indicator for establishing a relay-connectionbetween the relay nodes and the access node; and selecting, from theplurality of wireless devices, non-relay wireless devices for MU-MIMOpairing, wherein the selected non-relay wireless devices are prioritizedfor MU-MIMO pairing based on a channel orthogonality and SINR meeting aset threshold.
 2. The method of claim 1, further comprising: selectingat least one relay node from the excluded relay nodes for Single-UserMIMO scheduling.
 3. The method of claim 2, wherein the at least onerelay node is selected based on a reported Reference Signal ReceivedPower (“RSRP”), Received Signal Strength Indicators (“RSSI”), and RadioFrequency (“RF”) parameter.
 4. The method of claim 3, wherein datapackets are transmitted to the at least one relay node using aModulation and Coding Scheme (“MCS”) based on a Channel QualityIndicator (“CQI”) reported by the at least one relay node.
 5. The methodof claim 4, wherein data packets are scheduled to the at least one relaynode based a load at the relay node and an application profile ofend-users.
 6. The method of claim 2, wherein the at least one relay nodeis selected based on a loading condition.
 7. The method of claim 6,wherein the loading condition is based on a number of end-usersconnected to the at least one relay node.
 8. The method of claim 1,wherein excluding the relay nodes further comprises detecting arelay-connection between the relay nodes and the access node.
 9. Themethod of claim 1, further comprising detecting the relay nodes, whereinthe excluding further comprises excluding the detected relay nodes. 10.A system for enabling Multi-User Multiple-Input-Multiple-Output(MU-MIMO) pairing of wireless devices served by an access node, thesystem comprising: a processing node configured to: determine a channelorthogonality and Signal-to-Interference-Plus-Noise Ratio (SINR) of aplurality of wireless devices located in a geographic area served by theaccess node; exclude relay nodes located in the geographic area fromMU-MIMO pairing, wherein excluding the relay nodes comprises detecting arelay node capability indicator for establishing a relay-connectionbetween the relay nodes and the access node; and select, from theplurality of wireless devices, non-relay wireless devices for MU-MIMOpairing, wherein the selected non-relay wireless devices are prioritizedfor MU-MIMO pairing based on a channel orthogonality and SINR meeting aset threshold.
 11. The system of claim 10, wherein the processing nodeis further configured to: select at least one relay node from theexcluded relay nodes for Single-User MIMO scheduling.
 12. The system ofclaim 11, wherein the at least one relay node is selected based on areported Reference Signal Received Power (“RSRP”), Received SignalStrength Indicators (“RSSI”), and Radio Frequency (“RF”) parameter. 13.The system of claim 12, wherein data packets are transmitted to the atleast one relay node using a Modulation and Coding Scheme (“MCS”) basedon a Channel Quality Indicator (“CQI”) reported by the at least onerelay node.
 14. The system of claim 13, wherein data packets arescheduled to the at least one relay node based a load at the relay nodeand an application profile of end-users.
 15. The system of claim 11,wherein the at least one relay node is selected based on a loadingcondition.
 16. The system of claim 15, wherein the loading condition isbased on a number of end-users connected to the at least one relay node.17. The system of claim 10, wherein excluding the relay nodes furthercomprises detecting a relay-connection between the relay nodes and theaccess node.
 18. The system of claim 10, wherein the processing node isfurther configured to detect the relay nodes, and the excluding furthercomprises excluding the detected relay nodes.
 19. A method for selectingrelay nodes for Single-User Multiple-Input-Multiple-Output (SU-MIMO),the method comprising: determining a channel orthogonality andSignal-to-Interference-Plus-Noise Ratio (SINR) of a plurality ofwireless devices located in a geographic area of an access node;determining a relay status of the plurality of wireless devices;excluding non-relay wireless devices located in the geographic area fromSU-MIMO; and selecting relay nodes for SU-MIMO, wherein the selectedrelay nodes are prioritized for SU-MIMO based on a channel orthogonalityand SINR meeting a set threshold, wherein selecting the relay nodescomprises detecting a relay node capability indicator for establishing arelay-connection between the relay nodes and the access node.
 20. Themethod of claim 19, wherein selecting the relay nodes further comprisesdetecting a relay-connection between the relay nodes and the accessnode.